1. Field of the Invention
The present invention relates to marine vessels and more particularly relates to marine vessels that have a plurality of legs that can be raised or lowered, the legs having lower ends that engage the sea bed and powered elevating units for raising the vessel hull or barge on the legs so that the hull can be lifted free of the waters surface. Even more particularly, the present invention relates to an improved elevating system for use with jack-up rigs wherein a rack and pinion type elevating unit has an improved braking arrangement that places a motor drive and its planetary gear box on one side of a drive shaft of a pinion gear, the other side of the drive shaft carrying a brake drum and its band or disk brake arrangement with roller bearing being positioned in between the pinion gear and the planetary gear box on one side and a second roller bearing between the pinion gear and the brake drum hub and band on the other side.
2. General Background of the Invention
In the offshore oil and gas well drilling and production industry, it is common to use jack-up barges or jack-up rigs for many purposes. These rigs can be used to repair or work over oil and gas wells. Very large jack-up rigs are fitted as oil and gas well drilling rigs for drilling for oil and gas in a marine environment.
It is known in the art to use an elevating system for raising a barge relative to the legs of a jack-up rig using a rack and pinion type gearing mechanism. In such a case, a plurality of pinion gears engage a toothed rack mounted on each leg of the jack-up rig. It is also known to mount such a rack on a truss-type leg that is typically triangular or square in horizontal cross section or cylindrical pipe.
When using such a rack and pinion type elevating mechanism, there is a need for a brake system for locking the elevating unit relative to the leg when the hull is to be fixed at a desired position relative to the underlying waters surface.